This present study aimed to assess the effect of fermentation temperature and culture concentration on LAB growth, physical and chemical properties of fermenting cow and goat milk. The International Official Analytical Chemistry Association (AOAC) and the Indonesian National Standard (SNI) methods were used to analyze the physical and chemical properties of yogurt. Yogurt was prepared using fermentation temperature (40, 43, 46°C), a combination of Streptococcus thermophilus and Lactobacillus acidophilus strains. (1: 1), culture inoculation (5, 10, 15persent) and fermentation times (8 hours). The results showed that the cultures concentration and temperature have a significant effect on physicochemical properties, and viable amount of fermented milk samples. There were a significant difference (P< 0.05) between all yogurt samples in LAB growth, total solids, pH, viscosity, and there were no significant difference (P< 0.05 between, titeriatble acidity, color and density of all samples. The general results of this present study proved that the ideal state of fermentation of cow and goat milks fermentation were: fermentation 46°C, culture concentration 10, 15%, for 8h. Thus, the benefit from these results are developing physical and chemical properties and sensory characteristics of cow and goat milk yogurt.

Microbial load in fresh milk has a significant effect on its keeping quality and nutritional value. From Prehistoric time, human used heat process to reduce microbials load in raw milk to improve its sensory characteristics. This research is proposed to treat fresh goat milk with heating process to provide optimal pasteurization conditions that does not influence the goat milk chemical composition to suite production of goat yogurt powder. The pasteurization conditions considered were: Temperature (72, 80, and 85°C) and time (5, 10 and 15s). These results showed there were a significant difference (P<0.05) between treated milk and Indonesia national standards on viscosity and pH; whereas there was no significant differences on density and titratable acidity. The study results concluded that the temperature and time during heat processing had a significant effect on nutritional compounds of goat milk, with increase in lactose and non-fat solids contents; therefore, treated goat milk at 85°C to 5 s is better than other treatments.

Yogurt was a functional drink that was high in nutritional value but had a relatively short shelf life. Roselle extract had a high content of bioactive compounds, namely anthocyanin, polypHenol, and vitamin C. The integration of yogurt with roselle extract was expected to improve product performance both from the properties of health and sensory. This study aimed to determine the effect of roselle extract addition and fermentation time on the characteristics of roselle-based yogurt products.  The research method used was an experimental method with a completely randomized design with Duncan's further test with treatments (1) the addition of rosella extract consisted of 3 levels, namely 0.5, 1.5, and 2.5 %. (2) Fermentation time: 8, 12, and 16 hours. The observed variables included chemical (pH, total titrated acid/TTA, anthocyanins), microbiology (lactic acid bacteria/LAB), and sensory.  The fermentation time affects the pH value and TAT.  The 12 hours of fermentation time gave pH and TTA values, respectively: 3.77 and 1.23%. The variation in the addition of roselle extract significantly affected the anthocyanin, TTA, and LAB values. The addition of the extract as much as 1.5% gave the anthocyanins, TTA, and LAB value respectively 0.871 mg/mL, 1.31%, 561.11x 107CFU/mL.  The best treatment was yogurt with a roselle extract concentration of 1.5% and 20 hours of fermentation.  This yogurt had characteristic as follows: pH 3.7, TAT 1.33%, anthocyanins 0.8751 mg/mL, LAB 560 x 107 CFU/mL, reddish-yellow (4), distinctive aroma (4), Sour taste (4), fine texture (4), and liking (4).